Sewing Machine Drive

ABSTRACT

A magnetic encoder system of a sewing machine drive comprises a magnetic, magnetised disc with alternating north and south pole elements, which are used as incremental markings. The latter are designed as a full ring-incremental track, which extends around a circumference of the ferritic disc, and as an annular section incremental track, which is designed as an annular section on the ferritic disc. The result is a magnetic encoder system for a servomotor of a sewing machine.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the priority of German Patent Application, Serial No. 10 2015 226 666.4, filed Dec. 23, 2015, pursuant to 35 U.S.C. 199(a)-(d), the content of which is incorporated herein by reference as if fully set forth herein.

FIELD OF THE INVENTION

The invention relates to a sewing machine drive.

BACKGROUND OF THE INVENTION

Many different designs of sewing machine drives are known, for example from DE 19 714 520 A1.

SUMMARY OF THE INVENTION

An objective of the present invention is to develop a sewing machine drive so that with given security of a signal transmission the structural expense is reduced.

Said objective is achieved by a sewing machine drive with a magnetic encoder system

-   -   with a disc made from magnetic material, which is magnetised,     -   with alternating north and south pole elements, which are used         as incremental markings,         -   with a full ring incremental track, which extends as a ring             over 360° along a circumference of the disc,         -   with an additional annular section incremental track, which             is designed as an annular section on the disc.

According to the invention it has been found that such an arrangement has clear advantages. The disc can be connected in a rotationally secure manner to a rotatable shaft, in particular to a motor shaft. Particularly in motors, which are fixed for example to the upper part of a machine, it is expected that an encoder system belonging to the latter will get dirty to a certain degree, which makes visual checks more difficult for example. The incremental markings are in the form of a full ring incremental track over 360° around the circumference of the disc and an additional annular section incremental track, which covers a section of the disc. The magnetic incremental markings make it possible for example to reduce the cost of construction considerably, in particular of sealing an encoder housing, as dirt does not impair the magnetic flux. Advantageously, for this reason in particular no specially sealed bearings, e.g. for a shaft bearing, are required, which amounts to a considerable saving. The detectable signals of both incremental tracks can be assigned to independent signal evaluations. Also more than two incremental tracks can be used. Also more than two annular section incremental tracks can be used. Advantageously the individual annular section incremental tracks extend to different degrees on the circumferences of the disc, which for example makes it possible to recognise the direction of rotation. The incremental tracks can be applied to a top wall and/or a bottom wall of the disc. The incremental tracks can be attached onto an outer circumference of the disc. The incremental tracks can be applied to an outer casing wall of the disc. The disc can be made from ferritic material. The sewing machine drive can be designed as a servomotor. A sewing machine drive with a magnetic encoder system enables the optimised control of the drive, in particular a sewing machine motor, and can thus facilitate the handling of a sewing machine.

An encoder system is known from DE 39 90 206 T1. Further encoder systems are known from U.S. Pat. No. 4,551,676 A, US 2015/0091554 A1 and U.S. Pat. No. 4,987,040 A.

A ring incremental track, in which the full ring incremental track is used for determining the position and speed information, enables the secure determining of position and speed information without interference. Provided that a 1:1-translation is ensured between a rotor of the motor and the disc, the speed of a motor shaft of the motor corresponds to the speed of the magnetic disc.

An annular section incremental track, in which the annular section incremental track is used for zero point referencing, is used for the zero point referencing of the rotor.

The evaluation of the position and speed information of the ring incremental track, an evaluation unit with integrated microcontroller and magnet sensors performs the evaluation of the full ring incremental track, is performed by means of an evaluation unit with an integrated microcontroller and magnet sensors. This ensures a compact encoder system.

An additional, separate magnet sensor is used to detect the annular section incremental track. This sensor thus enables an independent zero point referencing.

The advantages of a sewing machine according to the invention corresponds to those already explained above with reference to the sewing machine drive.

Embodiments of the invention are explained in more detail in the following with reference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a perspective view of an encoder system assembly for attachment onto a servomotor of a sewing machine;

FIG. 2 shows a perspective plan view of the encoder system assembly;

FIG. 3 shows a perspective detailed view of a magnetic encoder system.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of a magnetic encoder system for a sewing machine drive in the form of a servomotor of a sewing machine is explained in the following with reference to FIGS. 1, 2 and 3.

An encoder system assembly 1 is used for securing a magnetic encoder system 2 to a servomotor for a sewing machine. The assembly 1 contains an attachment flange 3 next to the magnetic encoder system 2. By means of the attachment flange 3 the magnetic encoder system 2 is secured onto the servomotor. A motor shaft 4 of the otherwise not shown servomotor is guided through an opening in the attachment flange 3 and through the circular, central passage opening of the magnetic encoder system 2

A magnetic, in particular ferritic disc 5 of the magnetic encoder system 2 annularly surrounding the through opening is connected in a rotationally secure manner to the motor shaft 4 of the servomotor. On a plate 6 mounted additionally on the attachment flange 3 there is an evaluation unit 7. The latter is designed to be stationary relative to the attachment flange 3 (cf. FIG. 2).

The magnetic encoder system 2 comprises in addition to the evaluation unit 7 a full ring incremental track 8 and an annular section incremental track 9 (cf. FIG. 3). The full ring-incremental track 8 and the annular section incremental track 9 extend around a circumference of a magnetic disc 5, wherein the annular section incremental track 9 only comprises a portion of the circumference. Incremental tracks 8, 9 have alternating north pole elements 10 and south pole elements 11. The incremental tracks 8 and 9 are arranged coaxially relative to one another and to the motor shaft 4, wherein a radius R_(A) of the annular section incremental track 9 is smaller than a radius R_(V) of the full ring incremental track 8 (cf. FIG. 3).

The evaluation unit 7 is arranged opposite the magnetic disc 5 so that a first, not shown magnet sensor of the evaluation unit 7 detects the full ring-incremental track 8 and a further magnet sensor of the evaluation unit 7 not shown in detail detects the annular section incremental track 9. The two magnet sensors are arranged offset radially to one another.

Different, not shown additional variants of the encoder system assembly are possible.

Instead of exactly one annular section incremental track according to the annular section incremental track 9 of the embodiment described above, also more annular section incremental tracks can be provided. Circumferential extensions of the annular sections of said annular section incremental tracks can differ from one another. If in such a case for example two or three annular section incremental tracks with different circumferential extensions are provided, it is possible in principle to achieve a rotary direction detection with such a variant of the encoder system. In such a case two different types of circumferential extensions are sufficient. For example, a sequence of “short/long/long” can be distinguished from a sequence “long/long/short” for recognising the direction of rotation.

If a plurality of full ring incremental tracks are used, the latter can be arranged on different radius sections relative to the common axis of rotation. This facilitates a magnet sensor scanning of said incremental tracks. 

1. A sewing machine drive with a magnetic encoder system comprising: a disc made from magnetic material, wherein the disk is magnetised with alternating north and south pole elements, wherein the alternating north and south pole elements define incremental markings, a full ring incremental track, having incremental markings comprised of alternating north and south pole elements and arranged as a ring over 360° along a circumference of the disc and an additional annular section incremental track, having incremental markings comprised of alternating north and south pole elements and arranged as an annular section on the disc.
 2. The sewing machine drive according to claim 1 wherein the full ring incremental track is used for determining the position and speed information.
 3. The sewing machine drive according to claim 1, wherein the annular section incremental track is used for zero point referencing.
 4. The sewing machine drive according to claim 1, further comprising an evaluation unit with integrated microcontroller and magnet sensors performs the evaluation of the full ring incremental track.
 5. The sewing machine drive according to claim 1, wherein a further, separate magnet sensor is used to detect the annular section incremental track.
 6. The sewing machine drive according to claim 1 wherein one of the full ring incremental track and annular section incremental track is disposed radially outwardly of the other one of the full ring incremental track and annular section incremental track.
 7. The sewing machine drive according to claim 6, further comprising an evaluation unit comprised of a plurality of magnet sensors with one of the magnet sensors detecting the full ring incremental track and another one of the magnet sensors detecting the annular section incremental track.
 8. The sewing machine drive according to claim 7, wherein the evaluation unit is equipped with a microcontroller.
 9. The sewing machine drive according to claim 7, further comprising a rotary sewing machine drive shaft generally coaxial with one of the full ring incremental track and annular section incremental track.
 10. The sewing machine drive according to claim 1, further comprising a rotary sewing machine drive shaft about which the full ring incremental track generally coaxially extends.
 11. The sewing machine drive according to claim 10, wherein the annular section incremental track is disposed radially inwardly of the full ring incremental track between the full ring incremental track and the sewing machine drive shaft.
 12. The sewing machine drive according to claim 11, further comprising an evaluation unit comprised of a plurality of magnet sensors with one of the magnet sensors detecting the full ring incremental track and another one of the magnet sensors detecting the annular section incremental track.
 13. The sewing machine drive according to claim 1, further comprising: (a) a servomotor driven rotary sewing machine drive shaft about which (i) the full ring incremental track generally coaxially extends, and (ii) the annular section incremental track generally annularly extends, and (b) a processor-equipped evaluation unit comprised of a plurality of magnet sensors with one of the magnet sensors detecting alternating north and south poles of the full ring incremental track and another one of the magnet sensors detecting alternating north and south poles of the annular section incremental track.
 14. The sewing machine drive according to claim 1, further comprising: (a) a servomotor driven rotary sewing machine drive shaft about which (i) the full ring incremental track generally coaxially extends, and (ii) the annular section incremental track generally annularly extends, and (b) an evaluation unit configured to detect (i) north and south pole elements of the full ring incremental track, and (ii) north and south pole elements of the annular section incremental track.
 15. The sewing machine drive according to claim 14, wherein the disc is carried by the sewing machine drive shaft for rotation of the disc, the full ring incremental track, and the annular section incremental track substantially in unison therewith; and wherein the evaluation unit is mounted stationary relative to the sewing machine drive shaft, the full ring incremental track, and the annular section incremental track.
 16. The sewing machine drive according to claim 15, wherein the evaluation unit is configured to detect (i) north and south pole elements of the full ring incremental track for determining position and speed information thereof, and (ii) detecting north and south pole elements of the annular section incremental track for determining a zero point reference therefor.
 17. The sewing machine drive according to claim 16, wherein the evaluation unit comprised of a plurality of magnet sensors with one of the magnet sensors detecting north and south pole elements of the full ring incremental track for determining position and speed information thereof, and another one of the magnet sensors detecting north and south pole elements of the annular section incremental track for determining a zero point reference position therefor.
 18. A sewing machine drive with a magnetic encoder system comprising: (a) a servomotor-driven rotary sewing machine drive shaft; (b) a disc comprising a full ring incremental track comprised of alternating north and south pole elements defining one set of incremental markings, and an annular section incremental track comprised for alternating north and south pole elements defining another set of incremental markings; and (c) an evaluation unit configured to detect north and south pole elements of the full ring incremental track and north and south pole elements of the annular section incremental track during rotation of the sewing machine drive shaft.
 19. The sewing machine drive according to claim 18, wherein the disc is carried by the sewing machine drive shaft for rotation of the disc, the full ring incremental track, and the annular section incremental track substantially in unison with the sewing machine drive shaft; and wherein the evaluation unit is mounted stationary relative to the sewing machine drive shaft, the full ring incremental track, and the annular section incremental track.
 20. The sewing machine drive according to claim 19, wherein the evaluation unit is comprised of a plurality of magnet sensors with one of the magnet sensors detecting north and south pole elements of the full ring incremental track for determining position and speed information thereof, and another one of the magnet sensors detecting north and south pole elements of the annular section incremental track for determining a zero point reference position therefor. 